Osmotic Microbial Fuel Cell for Groundwater Softening, Defluoridation, Salinity Reduction, and Energy Production

Despite being the major source of freshwater, groundwater is contaminated with hardness, fluorides, salinity, and so on, and hence, its application for domestic/industrial purposes is severely limited. Existing remediation technologies demand both chemical and energy inputs. Therefore, in this study, an osmotic microbial fuel cell (OsMFC) was developed as an energy-positive and chemical-free technology to achieve simultaneous groundwater softening, defluoridation, salinity reduction, and bioelectricity production. High-quality water was extracted from wastewater in the OsMFC and was applied to reduce groundwater contaminants by dilution. The effects of feed/draw solution (FS/DS) ratio, membrane area, reactor volume, and time on water flux, energy production, and reduction efficiencies of ${\mathrm{Na}}^{+}$, ${\mathrm{Cl}}^{-}$, total hardness (TH), and ${\mathrm{F}}^{-}$ were studied. The increase in FS/DS ratio and membrane area resulted in considerable improvement in the water flux, energy production, and contaminant reduction. However, an increase in the reactor volume had little effect on the overall performance. A maximum water flux of 9.81 litres per square meter per hour [LMH (L/m²/h)] with reduction efficiencies of 75.81%, 76.27%, 72.22%, and 65.76% for ${\mathrm{Na}}^{+}$, ${\mathrm{Cl}}^{-}$, TH, and ${\mathrm{F}}^{-}$, respectively, were obtained with an extended operating time of 168 h. Maximum chemical oxygen demand (COD) removal of 86.6% and current density of ${0.34\mathrm{mA}/\mathrm{m}}^3$ were achieved simultaneously. The study demonstrated a sustainable approach of extracting high-quality water from wastewater and its application in groundwater remediation along with energy production.

In the present study, we have developed an osmotic microbial fuel cell (OsMFC), which is an in-house treatment system where groundwater remediation and wastewater treatment can be accomplished simultaneously with bio electricity generation. Compared with existing treatment techniques, OsMFC does not require the supply of chemicals and energy. It is a self-driven process with applications such as (1) water recovery; (2) bioelectricity generation; and (3) contaminant dilution using recovered water. The study established a sustainable methodology for extracting better-quality water from wastewater and its application in groundwater contaminant reduction.